Multi-layer filter webs, which usually consist of a filter material containing fibres, are of sufficiently known art. The bonding of individual filter layers of the filter web thereby usually takes place via edgewise welding or the use of adhesive. Filter layers of this type, with individual filter layers adhered or welded to one another, can then in a further operation, for example, be wound up to form a wound filter. The bonding techniques that are deployed, that is to say in particular the above-cited use of adhesive and/or welding to bond the individual filter layers of the filter web, are complex in production terms, and thus expensive, and moreover often generate only unsatisfactory bonding between the individual layers of the filter web.
From DE 20 2005 019 910 U1 a generically similar filter web is of known art, in which the two filter layers are, however, bonded together in a form fit manner, for example, by means of overlapping and subsequent stamping, that is to say therefore, macroscopically.